//Define libraries
#include <PubSubClient.h>
#include <WiFi.h>

int led_pin = 5;
char client_id[50];
WiFiClient espClient;
PubSubClient Client(espClient);

void setup() 
{
  Serial.begin(115200);
  pinMode(led_pin, OUTPUT);

  WiFi.mode(WIFI_STA);
  WiFi.begin("Woki-GUEST", "");

  Client.setServer("broker.emqx.io", 1883);
  Client.setCallback(callback);
}

void mqttReconnect() 
{
  while (!Client.connected())
  {
    Serial.print("Attempting MQTT connection...");
    if(Client.connect(client_id))
    {
      Serial.println("Connected");
      Client.subscribe("topicName");
    }
    else
    {
      Serial.print("Connection failed, try again!");
      delay(5000);
    }
  }

}

void callback(char* topic, byte* message, unsigned int length) 
{
  String stMessage;
  for (int i = 0; i < length; i++) 
  {
    stMessage += (char)message[i];
  }
  if(stMessage == "off")
  {
    digitalWrite(led_pin, LOW);
    Serial.print("LIGHT OFF!");
  }
  if(stMessage == "on")
  {
    digitalWrite(led_pin, HIGH);
    Serial.print("LIGHT ON!");
  }
  else
  {
    Serial.print("INVALID COMMAND!");
  }
}

void loop() 
{
  delay(10000);
  if(!Client.connected())
  {
    mqttReconnect();
  }
  Client.loop();
}